Up to the present, the particulate mineral base material used for manufacturing moulds and cores has practically exclusively been quartz sand.
Admittedly, it is not unknown within the foundry industry also to use other particulate mineral base materials such as olivine sand, a magnesium-iron silicate, and zircon sand, a zirconium silicate. Due to their high resistance to heat and their high price, these base materials have especially found localized use as so-called "pattern sand" or as a core inlay in such regions of moulds for casting steel castings that are particularly exposed to heat, so as to avoid or reduce the "burning-on" of sand on corresponding regions of the castings and the consequent cumbersome and costly cleaning of the castings.
A corresponding use has been found for crushed chromite ore, as with this mineral it is also the case that its wetting relations towards liquid steel are such, that it simply "repels" the latter.
No examples are known of such particulate mineral base materials having been used in a larger mass of circulating mould material, let alone for casting non-ferrous metals or alloys.
In a paper (38th International Foundry Congress, Exchange Paper No. 9, Dusseldorf, 1971) "Moglichkeiten der industriellen Anwendung des Magnetformverfahrens zur Herstellung von Massengussteilen" by A. Wittmoser, K. Steinack and R. Hofman, mass production of castings is described, based on a mass production of heat-gasifiable patterns of expanded polystyrene foam. These patterns are covered by being sprayed with or dipped into a coating (Schlichte), after which they are enveloped with a flowable mixture of iron granulate and crushed magnetite ore, possibly in a fluidized state. Prior to the casting operation, a magnetic field is applied to the mould material so as to bond its individual particles together magnetically, said field being maintained during the casting proper and at least a part of the time, during which the metal solidifies in the mould. When the magnetic field has been removed, the mould material, now again being flowable, flows away from the casting, after which it may be used in new moulds, possibly after having been cooled. The paper, exclusively relating, to the casting of ferrous alloys, mentions the higher cooling effect of the mould material as compared to quartz sand, and also discusses how this cooling effect may be varied by changing the quantitative ratio between iron granulate and magnetite particles in the mould material, so that an increased proportion of magnetite particles reduces the cooling effect.
Obviously, this method cannot be used in a conventional moulding and casting system.
For casting light-metal castings, especially for use in the automotive and similar industries, there is, however, a great need for achieving a more rapid cooling of the metal having been cast in the mould, as this makes it possible to achieve a more fine-grained structure in the casting and also to avoid so-called micro-contraction cavities in the castings.
At the present time, attempts are made to achieve such more rapid cooling by casting in so-called metallic moulds (dies). Such moulds are, however, costly to manufacture, and in comparison with casting in a conventional moulding and casting system based on the use of sand, their productive capacity is very limited.